Facebook covertly uses your iPhone's camera while you're browsing your feed
Discovered by Joshua Maddux, the issue only affects iPhones running iOS 13.2.2, so if your iPhone hasn't been updated or you're using an Android smartphone, you should be safe. The Next Web reports that it's been able to reproduce the issue, which seems to affect only certain iPhones.
Judging by its behavior, this appears to be no more than a bug, which we hope will be addressed by Facebook sooner rather than later. If you're using an iPhone powered by iOS 13.2.2, you might notice that the camera feed is shown in a small sliver on the left side of the screen right after you open a photo in the app and swipe down.
Found a @facebook#security & #privacy issue. When the app is open it actively uses the camera. I found a bug in the app that lets you see the camera open behind your feed. Note that I had the camera pointed at the carpet. pic.twitter.com/B8b9oE1nbl— Joshua Maddux (@JoshuaMaddux) November 10, 2019
Now, as Maddux suggests, even though he wasn't able to reproduce the bug on iPhones running iOS 12, it doesn't mean that it might not be there, it's just that it's not visible. Although we believe this is a bug, it's unclear if this is the intended behavior of the software.
The important thing is that you can prevent it from happening by revoking Facebook's access to your iPhone's camera. When camera permission is disabled, iOS will automatically prevent Facebook from accessing the camera, so you should be safe in theory.